Imaging sensor systems are routinely employed in military applications to provide information used in surveillance or in the guidance of a weapon system to a particular target. Such systems typically employ a scanning electro-optic sensor sensitive to certain portions of the electromagnetic spectrum. Such sensors are thus able to discriminate the emitted radiation of various target features in the sensor field-of-view.
A common prior art electro-optic sensor employs a linear array of infrared sensors. The linear array is combined with imaging optics and a scanning mirror such that it can be swept through a specific angle representing a field-of-view while the electrical output of each detector element is sampled at discrete intervals to form a set of "M" samples. In this manner, the field-of-view is quantized into a set of samples comprising N-rows by M-columns. It is the task of the image processor to analyze each set of input data, to determine if a particular object is present in the field-of-view and, if present, to determine, in effect, its coordinate location. Although a variety of techniques for such processing has been proposed and practiced, the most effective and widely used is to employ what is known as template matching.
In this arrangement, features of the object or objects of interest are stored as a digital template and are systematically compared to the input data from the sensor array. This is a very demanding and computationally intensive task in that to perform the template match, the template must be shifted for each condition of variability which may exist in the field-of-view. At a minimum, the template must be translated for all possible X-Y coordinate conditions that it might be found in the field-of-view. Additionally, the template may also have to be tested for various values of size commensurate with various ranges from the sensor to the object. Further, if the rotational position of the object is unknown, the template must be varied for all conditions of rotational orientation.
Although template matching algorithms have been extensively developed for implementation in general purpose programmable computers, such implementations are typically not practical for real-time, low-cost, low-power and very small size systems which could be deployed in a weapon guidance system, for example.